Center-filled chewing gums are well known in the art. U.S. Pat. No. 4,156,740 to Glass et al. discloses a sugarless center-filled chewing gum which has incorporated in both the chewing gum shell and the center-fill a composition which contains: from 0.4 to 1 part by weight of a natural or synthetic gum; from 50 to 84 parts by weight of a glycerin humectant; and from 15 to 49.6 parts by weight of an additional water-miscible humectant ingredient which is sorbitol solution or sobitol solution and propylene glycol.
U.S. Pat. No. 4,466,983 to Cifrese et al. discloses a center-filled chewing gum having a sugarless, semi-liquid center-fill which includes a hydrogenated starch hydrolysate, sorbitol solution, glycerin and optional flavoring, wherein the total water content of the semi-liquid center-fill is less than about 5% by weight.
U.S. Pat. No. 4,250,196 to Friello, discloses a liquid center-fill which is an aqueous solution consisting essentially of hydrogenated starch hydrolysate present in the solution as a solid in an amount of about 75 to about 93% by weight of the liquid fill.
U.S. Pat. No. 4,316,915 to Friello et al. discloses a sugarless center-filled chewing gum having a liquid fill consisting essentially of from about 94% to 99.5% glycerin and about 0.5 to 6% by weight of a thickener, the water content of the center-fill being no more than about 2% or less.
U.S. Pat. No. 3,894,154 to Graff et al. discloses a center-filled chewing gum which includes, as a liquid fill, an aqueous solution having a dissolved solids portion and a water-miscible humectant for retarding increases in the viscosity of the center fill. The humectant is glycerin, and the dissolved solids portion may include invert sugar, sucrose and glucose. British Pat. No. 1,469,031 discloses a center-filled chewing gum similar to that disclosed in U.S. Pat. No. 3,894,154 except that the humectant may be glycerin, polylimonene, sorbitol solution, lecithin, dextrose, gum arabic, glyceryl monostearate, polyethylene glycol or propylene glycol.
U.S. Pat. No. 4,292,329 to Ogawa et al. discloses a method of improving the flavor-retaining capacity of a center-fill chewing gum by incorporating into the center-fill an emulsifier which functins both as an emulsifier and retention agent to prevent the flavor from penetrating into the gum base. The liquid fill generally contains from 5 to 10% of water. U.S. Pat. No. 4,157,402 to Ogawa et al. also teaches the use of an emulsifier for similar purposes but requires the emulsifier to have a particular hydrophile-lipophile (HLB) range.
U.S. Pat. No. 4,252,829 to Terrevazzi discloses a liquid fill for center-filled chewing gum consisting essentially of an aqueous solution containing a dissolved solid portions, 8 to 13% liquid sorbitol and 2 to 5% of a propylene glycol-flavor solution.
Substantially anhydrous sugarless chewing gums are also known in the art. U.S. Pat. No. 4,514,422 to Yang et al. discloses sugarless gums, including chewing gums and bubble gums, having improved shelf-life and resistance to staling, which contain a substantially anhydrous mixture of a gum base, at least one sugar alcohol and glycerin wherein the glycerin is present in amounts of about 8% to about 18% by weight, and wherein the gum contains no greater than 2% by weight thereof, of water in any form.
U.S. Pat. No. 4,581,234 to Cherukuri et al. discloses a chewing gum composition having a moisture content up to about 0.3% by weight, containing a gum base which softens within a temperature range of about 40.degree. C. to about 60.degree. C., flavoring, a softener and a sweetener, and teaches that such chewing gum compositions have exceptionally long periods of shelf-life.
U.S. Pat. No. 3,806,290 and U.S. Pat. No. 3,857,963 to Graft et al., discloses a continuous method and apparatus for extruding chewing gum to form a hollow-centered rope of gum and forcing the center-fill into the cavity within the rope of gum.
The above prior art diclosures indicate that when the amount of moisture in a chewing gum composition, whether it be a sugar containing or sugarless gum, is reduced, the stability and hence the shelf-life of the gum is increased. In addition, certain ingredients which deteriorate rapidly in the presence of water, may be used with substantially anhydrous chewing gums. Thus, there are a number of commercial advantages attendant upon the use of substantially anhydrous chewing gums. Although such gums are extrudable and could be used to form the shell of a center-fill sugarless chewing gum, prior art sugarless center-fills have not been used successfully within the cavity of a substantially anhydrous chewing gum shell. The current sugarless center-fills either contain too much water and migrate into the chewing gum shell or are too viscous to be pumped into the hollow center of the chewing gum shell as is required in continuous commercial processes used for making center-filled gum.